A photocatalyst pretreatment flue gas denitrification device and intelligent monitoring method thereof

Abstract

The present application relates to a photocatalytic pretreatment flue gas denitrification device and an intelligent monitoring method thereof, belonging to the technical field of flue gas treatment devices. The flue gas denitrification device comprises: a pretreatment tower, the pretreatment tower being provided with an air inlet pipe, the pretreatment tower being provided with a photocatalytic catalytic system, the photocatalytic catalytic system being used to oxidize nitrogen oxides in the flue gas; a wet absorption box, the wet absorption box being provided with a denitrification absorption liquid, the wet absorption box being provided with an exhaust pipe and a liquid drain pipe; a flue gas duct assembly being used to connect the pretreatment tower and the wet absorption box, with the air outlet end of the flue gas duct assembly being provided below the liquid level of the denitrification absorption liquid. The present application has the effect of improving the efficiency of wet flue gas denitrification treatment; and introduces fuzzy control, which is combined with PID parameter adjustment to form an adaptive fuzzy PID algorithm, realizing the functions of intelligent monitoring of the flue gas after denitrification and providing data collection, processing, analysis and feedback.

Description

Technical Field

[0001] The present application relates to the field of flue gas treatment devices, and in particular to a photocatalyst pretreatment flue gas denitrification device and an intelligent monitoring method thereof. Background Art

[0002] my country is the world's major coal producer and consumer. The environmental pollution caused by coal-based power production is a constraint on the development of my country's power industry. According to relevant standards, there are strict requirements on the nitrogen oxide emissions of thermal power units.

[0003] Wet flue gas treatment technology is a traditional flue gas treatment technology with simple process, low investment, good treatment effect and a wide range of absorbents available for application. However, wet flue gas denitrification technology has been progressing slowly, mainly due to the special properties of flue gas. The O2 content in flue gas is only 6-9%, and NO x The concentration is relatively low, so NO in flue gas x The degree of oxidation is very low, that is, 90-95% of NO in the flue gas x For NO, by NO x The study of liquid phase reaction mechanism found that NO x The liquid phase absorption is first transferred from the gas phase to the water phase, which is mainly achieved through the absorption equilibrium of the gas in the solution, and the absorption equilibrium conforms to Henry's law.

[0004] However, NO has a very low solubility in water, which significantly increases the mass transfer resistance of liquid-phase absorption. Modifying the temperature and pH of the solution, among other methods, fails to significantly increase NO solubility in water. This characteristic results in a series of problems with current wet flue gas denitrification technologies, such as low removal efficiency and high energy consumption, making it difficult to achieve true industrial application. Summary of the Invention

[0005] In order to improve the treatment efficiency of wet flue gas denitrification, the present application provides a photocatalyst pretreatment flue gas denitrification device and an intelligent monitoring method thereof.

[0006] In the first aspect, the present application provides a photocatalyst pretreatment flue gas denitrification device, which adopts the following technical solution: a photocatalyst pretreatment flue gas denitrification device, comprising: a pretreatment tower, the pretreatment tower is provided with an air inlet pipe, the pretreatment tower is provided with a photocatalyst catalytic system, and the photocatalyst catalytic system is used to oxidize nitrogen oxides in the flue gas; a wet absorption box, the wet absorption box is provided with a denitrification absorption liquid, and the wet absorption box is provided with an exhaust pipe and a drain pipe; a flue gas duct assembly, which is used to connect the pretreatment tower and the wet absorption box, and the air outlet end of the flue gas duct assembly is provided below the liquid level of the denitrification absorption liquid.

[0007] By adopting the above technical solution, the flue gas to be treated first passes into a pretreatment tower, where a photocatalytic system catalyzes the oxidation of nitrogen oxides in the flue gas. The oxidized flue gas then enters a wet absorption tank where it comes into contact with a denitrification absorbent solution, which absorbs the nitrogen oxides in the flue gas. The treated flue gas is then discharged through the exhaust pipe. The photocatalytic system oxidizes the poorly water-soluble NO into a high-valent state, increasing the water solubility of the nitrogen oxides in the flue gas and thereby improving the efficiency of wet flue gas denitrification.

[0008] Optionally, the photocatalytic system includes a catalyst carrier plate and an ultraviolet light source arranged in a pretreatment tower, and a photocatalytic coating is provided on the surface of the catalyst carrier plate.

[0009] By adopting the above technical solution, the flue gas enters the pretreatment tower and comes into contact with the catalytic carrier plate. The photocatalyst coating on the catalytic carrier plate catalytically oxidizes the nitrogen oxides in the flue gas under the irradiation of the ultraviolet light source, thereby achieving the purpose of increasing the oxidation degree of nitrogen oxides in the flue gas.

[0010] Optionally, the catalytic carrier is hollow inside and has a plurality of vent holes, and there are multiple catalytic carriers. One end of the multiple catalytic carriers is connected to the same rotating shaft, and the pretreatment tower is provided with a driving component for driving the rotating shaft to rotate.

[0011] By adopting the above technical solution, the interior of the catalytic carrier is hollow and provided with ventilation holes, which increases the surface area available for the photocatalytic coating to adhere and the contact area with the flue gas; and when the driving component drives the rotating shaft to rotate, the turbulence of the flue gas in the pretreatment tower can be increased, and the flue gas can more easily enter the interior of the catalytic carrier through the ventilation holes; in addition, during the rotation of the catalytic carrier, the rotation angle of the catalytic carrier changes continuously, the ultraviolet light received at various locations is more balanced, and the ultraviolet light can more easily be irradiated into the interior of the catalytic carrier through the ventilation holes, thereby triggering the photocatalytic coating to catalytically oxidize the nitrogen oxides in the flue gas, thereby improving the oxidation efficiency of the nitrogen oxides in the flue gas.

[0012] Optionally, a reflective film is provided on the inner wall of the pretreatment tower.

[0013] By adopting the above technical solution, the reflective film is used to reflect ultraviolet light, and the ultraviolet light irradiated on the inner wall of the pretreatment tower is reflected onto the catalytic carrier plate, thereby improving the utilization efficiency of ultraviolet light.

[0014] Optionally, a dust reduction component is provided in the pretreatment tower, and the dust reduction component is arranged between the air intake pipe and the photocatalytic system. The dust reduction component includes a dust shield, and the dust shield is arranged on the inner wall of the pretreatment tower. The dust shield is arranged to be tilted downward at one end away from the inner wall of the pretreatment tower.

[0015] By adopting the above technical solution, the dust shield can block the upward movement of the flue gas, and at the same time block the larger fly ash contained in the flue gas, thereby reducing the fly ash content in the flue gas and reducing the occurrence of dust accumulation on the catalytic carrier covering the photocatalyst coating, so as to ensure the contact area between the photocatalyst coating and the flue gas; when a large amount of fly ash is attached to the dust shield, since one end of the baffle is tilted downward, the accumulated fly ash can slide downward by its own weight and along the tilt trend of the dust shield, so that it is not easy for too much dust to accumulate on the dust shield.

[0016] Optionally, a cyclone assembly is provided in the pretreatment tower, and the cyclone assembly is provided between the air inlet pipe and the dust shield. The cyclone assembly includes an inner ring plate, a guide plate and an outer ring plate. One end of the guide plate is fixed to the inner ring plate and multiple guide plates are evenly arranged along the circumference of the inner ring plate, and the other end is fixed to the outer ring plate. Multiple guide plates are stacked and inclined, and the outer ring plate is fixed to the inner wall of the pretreatment tower.

[0017] By adopting the above technical solution, when the flue gas passes through the cyclone component, it will be guided by the guide plate and rotated to form a cyclone. The guide plate can block the movement path of fly ash in the flue gas and increase its contact time with the flue gas, so that the fly ash can be prevented from falling by the cyclone, thereby achieving the purpose of flue gas dust removal. The fly ash blocked by the dust reduction component, i.e., the cyclone component, can fall into the ash collecting hopper for subsequent centralized treatment.

[0018] Optionally, the dust reduction component also includes a filter for filtering fly ash in the flue gas, the filter is arranged between the dust guard plate and the photocatalytic system, the lower surface of the filter is provided with a first self-cleaning coating, and the inclined top surface of the dust guard plate and the guide plate is provided with a second self-cleaning coating.

[0019] By adopting the above technical solution, the flue gas is further filtered through the filter, effectively reducing the fly ash content in the flue gas; the fly ash adheres to the bottom of the filter when it contacts the filter, and since the flue gas is accompanied by water vapor, the water vapor condenses into water droplets when it encounters the filter. Through the setting of the first self-cleaning coating, the water droplets can easily drip from the filter and at the same time take away the fly ash on the filter, ensuring the surface cleanliness of the filter and preventing excessive dust accumulation on the surface, thereby ensuring the filtering efficiency of the filter for the flue gas.

[0020] Optionally, a cold source component is provided on the filter mesh, and the cold source component includes a cold flow tube provided on the filter mesh, the cold flow tube is provided with a continuous bend, one end of the cold flow tube is provided with a liquid inlet, and the other end is provided with a liquid outlet, the liquid inlet is connected to an external tap water pipe, and the liquid outlet is provided above the filter mesh.

[0021] By adopting the above technical solution and setting up the cold source component, water vapor in the flue gas is more likely to condense when it hits the filter, and the first self-cleaning coating is more likely to achieve a self-cleaning effect; at the same time, the water discharged from the liquid outlet can pass through the filter to clean the filter and the dust reduction component below, reducing the accumulation of dust on the filter and the dust shield.

[0022] Optionally, the flue gas duct assembly includes a main air duct, a connecting air duct and multiple sub-air ducts connected in sequence, the end of the main air duct away from the sub-air duct is connected to the top of the pretreatment tower, the end of the sub-air duct away from the main air duct extends below the liquid level of the wet absorption box, and the bottom of the sub-air duct is provided with a waterproof and breathable membrane.

[0023] By adopting the above technical solution, the flue gas after oxidation passes through the main air duct, the connecting air duct and the sub-air duct in sequence, and the denitrification efficiency of the flue gas is improved by adding multiple sub-air ducts; in addition, the flue gas can enter the denitrification absorption liquid through the waterproof breathable membrane, while the denitrification absorption liquid cannot enter the sub-air duct through the waterproof breathable membrane, thereby increasing the path for the flue gas to emerge from the denitrification absorption liquid, allowing the nitrogen oxides in the flue gas to fully contact the denitrification absorption liquid, thereby making the denitrification of the flue gas more thorough.

[0024] In a second aspect, the present application also provides an intelligent monitoring method for photocatalytic pretreatment flue gas denitrification, which adopts the following technical solution:

[0025] An intelligent monitoring method for photocatalytic pretreatment flue gas denitrification comprises the following steps:

[0026] S1: Collect the actual measurement value of the nitrogen oxide detector in real time, compare it with the set safe emission value, and calculate the deviation value of nitrogen oxides in the exhaust gas and the change rate of the deviation value;

[0027] S2: Input the deviation value and deviation change rate of nitrogen oxides in the exhaust gas from the exhaust pipe into the fuzzy controller to determine the nitrogen oxide deviation, deviation change rate, and proportional change value Δk p , integral change value Δk i , differential change value Δk d The membership function of

[0028] S3: According to the fuzzy control rules, output the new fuzzy set membership function and calculate the proportional change value Δk accordingly p , integral change value Δk i , differential change value Δk d ;

[0029] S4: Use proportional change value Δk p , integral change value Δk i , differential change value Δk dAdjust the corresponding proportional parameters, integral parameters, and differential parameters in PID in real time to obtain new PID parameters;

[0030] S5: Based on the new PID parameters, the opening and closing degree of the valve body at the intake pipe is controlled to control the flue gas flow in the intake pipe.

[0031] By adopting the above technical solution and using a fuzzy control algorithm to adjust the parameters of PID control, combined with the PID control algorithm, on the one hand, it is possible to avoid the situation where the nitrogen oxide content in the gas discharged from the exhaust pipe exceeds the standard from time to time; on the other hand, it is possible to more reasonably and efficiently control the flue gas flow in the intake pipe, thereby improving the efficiency of flue gas treatment.

[0032] In summary, this application includes at least one of the following beneficial technical effects:

[0033] 1. Through the setting of the photocatalytic system, the water-insoluble NO is oxidized into a high-valent state, thereby increasing the water solubility of nitrogen oxides in the flue gas, thereby improving the treatment efficiency of wet flue gas denitrification;

[0034] 2. The reflective film is used to reflect ultraviolet light, which is irradiated on the inner wall of the pretreatment tower and reflected onto the catalytic carrier plate, thereby improving the utilization efficiency of ultraviolet light;

[0035] 3. Through the setting of the waterproof breathable membrane, the flue gas can enter the denitrification absorption liquid through the waterproof breathable membrane, while the denitrification absorption liquid cannot enter the sub-air duct through the waterproof breathable membrane, which increases the path for the flue gas to emerge from the denitrification absorption liquid, so that the nitrogen oxides in the flue gas are fully in contact with the denitrification absorption liquid, thereby making the denitrification of the flue gas more thorough. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present application.

[0037] Figure 2 It is a cross-sectional view showing the internal structure of the pretreatment tower in the embodiment of the present application.

[0038] Figure 3 It is a cross-sectional view showing the internal structure of the wet absorption box in the embodiment of the present application.

[0039] Figure 4 It is a structural schematic diagram of the dust reduction component and the cold source component in the embodiment of the present application.

[0040] Figure 5 It is a schematic diagram of the structure of the cyclone assembly in the embodiment of the present application.

[0041] Figure 6 It is a structural diagram of the photocatalytic system and driving components in the embodiment of the present application.

[0042] Figure 7 It is a cross-sectional view showing the specific structure of the catalytic carrier plate in the embodiment of the present application.

[0043] Figure 8 It is a cross-sectional view of the nitrogen oxide detector in the embodiment of the present application.

[0044] Explanation of reference numerals: 1. Pretreatment tower; 11. Air inlet pipe; 12. Ash hopper; 121. Discharge valve; 13. Mounting frame; 14. Reflective film; 2. Wet absorption box; 21. Exhaust pipe; 211. Nitrogen oxide detector; 22. Drain pipe; 3. Flue gas duct assembly; 31. Main air duct; 32. Connecting air duct; 33. Sub-air duct; 331. Waterproof and breathable membrane; 4. Photocatalyst catalytic system; 41. Catalytic carrier plate; 411. Photocatalyst coating; 412. Vent ; 42. Ultraviolet light source; 43. Rotating shaft; 431. Second bevel gear; 5. Dust reduction assembly; 51. Dust shield; 511. Second self-cleaning coating; 52. Filter; 521. First self-cleaning coating; 6. Cyclone assembly; 61. Inner ring plate; 62. Guide plate; 63. Outer ring plate; 7. Cold source assembly; 71. Cold flow pipe; 711. Liquid inlet; 712. Liquid outlet; 8. Drive assembly; 81. Drive motor; 82. Drive shaft; 821. First bevel gear. DETAILED DESCRIPTION

[0045] The following is combined with Figure 1-8 , further details of this application are given.

[0046] In a first aspect, embodiments of the present application disclose a photocatalyst pretreatment flue gas denitrification device.

[0047] Reference Figure 1 and Figure 2 A photocatalytic pretreatment flue gas denitrification device includes a pretreatment tower 1 and a wet absorption box 2. The pretreatment tower 1 and the wet absorption box 2 are connected through a flue gas duct assembly 3. An air inlet pipe 11 is fixedly connected to the side wall of the pretreatment tower 1. A photocatalytic catalytic system 4 is provided in the pretreatment tower 1. The photocatalytic catalytic system 4 is used to oxidize nitrogen oxides in the flue gas. Denitrification absorption liquid is stored in the wet absorption box 2. The outlet end of the flue gas duct assembly 3 is located below the liquid level of the denitrification absorption liquid. An exhaust pipe 21 is fixedly connected to the side wall of the wet absorption box 2. The exhaust pipe 21 is used to discharge the treated flue gas. The denitrification absorption liquid can also be added to the wet absorption box 2 through the exhaust pipe 21. The exhaust pipe 21 is located above the liquid level of the denitrification absorption liquid. A drain pipe 22 is fixedly connected to the bottom end of the side wall of the wet absorption box 2 for discharging the denitrification absorption liquid after absorbing the flue gas.

[0048] Reference Figure 3In this embodiment, the denitrification absorption liquid can be a traditional absorption liquid used for wet absorption: alkaline solution absorption liquid, liquid-phase oxidation absorption liquid, liquid-phase reduction absorption liquid, etc. In order to facilitate the discharge of the denitrification absorption liquid that has absorbed nitrogen oxides, the inner bottom wall of the wet absorption box 2 is gradually tilted downward in the direction close to the drain pipe 22.

[0049] Reference Figure 2 and Figure 4 A dust reduction component 5 is provided in the pretreatment tower 1. The dust reduction component 5 includes a plurality of dust shields 51. The plurality of dust shields 51 are arranged in an array from bottom to top on the inner wall of the pretreatment tower 1. The dust shield 51 is arranged above the air inlet pipe 11, and the end of the dust shield 51 away from the inner wall of the pretreatment tower 1 is tilted downward.

[0050] Reference Figure 2 and Figure 5 A cyclone assembly 6 is also provided in the pretreatment tower 1 between the air inlet pipe 11 and the dust shield 51. The cyclone assembly 6 includes an inner ring plate 61, multiple guide plates 62 and an outer ring plate 63 installed on the inner wall of the pretreatment tower 1. The inner ring plate 61 is concentrically arranged with the outer ring plate 63. One end of the guide plate 62 is fixedly connected to the inner ring plate 61 and is evenly arranged along the circumference of the inner ring plate 61. The other end is fixedly connected to the outer ring plate 63, and multiple guide plates 62 are stacked and inclined.

[0051] Reference Figure 1 and Figure 2 An ash hopper 12 is installed at the bottom of the pretreatment tower 1. The ash hopper 12 is connected to the interior of the pretreatment tower 1, and a discharge valve 121 is installed at the bottom of the ash hopper 12. After the flue gas enters the pretreatment tower 1 from the air inlet pipe 11, when the flue gas passes through the cyclone assembly 6, the larger fly ash particles in the flue gas are blocked by the guide plate 62 and fall down under the influence of their own weight. When they move upward, they will pass through the cyclone assembly 6 along the inclined direction of the guide plate 62 to form a cyclone, and will be further blocked by the dust shield 51, thereby effectively reducing the content of fly ash in the flue gas and achieving dust reduction of the flue gas. At the same time, the end of the dust shield 51 away from the inner wall of the pretreatment tower 1 is tilted downward, so that the fly ash accumulated on the inclined bottom can quickly fall into the ash hopper 12.

[0052] Reference Figure 2 and Figure 4The dust reduction component 5 also includes a filter 52 disposed above the dust shield 51, and the lower surface of the filter 52 is coated with a first self-cleaning coating 521. In this embodiment, the first self-cleaning coating 521 is a fluorinated titanium dioxide nanoparticle coating. When the flue gas passes through the filter 52, the fly ash particles remaining in the flue gas are filtered by the filter 52, further improving the dust reduction effect on the flue gas, so as to prevent the dust particles in the flue gas from adhering to the photocatalytic system 4 and affecting the oxidation efficiency of nitrogen oxides in the flue gas. At the same time, the flue gas is often accompanied by water vapor. Through the provision of the first self-cleaning coating 521, water droplets can easily drip from the filter 52 and at the same time carry away the fly ash on the filter 52, ensuring the surface cleanliness of the filter 52 and preventing excessive dust accumulation on the surface, thereby ensuring the filtering efficiency of the filter 52 for the flue gas.

[0053] Reference Figure 2 and Figure 4 To prevent dust particles accompanying the dripping water from adhering to the dust shield 51 and guide plate 62 below, thereby affecting the guide plate 62's diversion function, the inclined top surfaces of the dust shield 51 and guide plate 62 are coated with a second self-cleaning coating 511. In this embodiment, the second self-cleaning coating 511 is also a fluorinated titanium dioxide nanoparticle coating.

[0054] Reference Figure 2 and Figure 4 To facilitate condensation of water vapor in the flue gas as it passes through the filter 52, thereby enhancing the self-cleaning effect of the filter 52, the filter 52 is made of a metal material with high thermal conductivity. A cold source assembly 7 is provided on the filter 52. The cold source assembly 7 includes a cold flow pipe 71 fixed to the top of the filter 52. The cold flow pipe 71 is arranged in a continuously curved "S" shape to increase the effective cooling path of the cold flow pipe 71. A liquid inlet 711 is provided at one end of the cold flow pipe 71, and a liquid outlet 712 is provided at the other end. The liquid inlet 711 is connected to an external tap water pipe, and the liquid outlet 712 is provided within the pretreatment tower 1 and above the filter 52. In this way, the tap water entering the condenser through the liquid inlet 711 absorbs heat and cools the filter 52, causing the water vapor in the flue gas to condense and then be discharged from the liquid outlet 712; and the water discharged from the liquid outlet 712 can pass through the filter 52 to clean the filter 52 and the dust baffle 51 and guide plate 62 below, and cooperate with the strong hydrophobic performance of the second self-cleaning coating 511 to achieve the self-cleaning effect of the dust baffle 51 and the guide plate 62.

[0055] Reference Figure 2 、 Figure 6 and Figure 7The photocatalytic system 4 includes a catalytic carrier plate 41 and an ultraviolet light source 42 arranged in the pretreatment tower 1. The surface of the catalytic carrier plate 41 is coated with a photocatalytic coating 411. There are multiple catalytic carrier plates 41, and one end of the multiple catalytic carrier plates 41 is fixedly connected to the same rotating shaft 43, which is arranged in the vertical direction. A mounting bracket 13 is fixed on the inner wall of the pretreatment tower 1, and the rotating shaft 43 is rotatably connected to the mounting bracket 13. The pretreatment tower 1 is provided with a drive assembly 8 that drives the rotating shaft 43 to rotate. The drive assembly 8 includes a drive motor 81 and a drive shaft 82. The drive motor 81 is installed on the outer wall of the pretreatment tower 1, and the drive shaft 82 is rotatably connected to the side wall of the pretreatment tower 1. One end of the drive shaft 82 is coaxially fixed with a first bevel gear 821, and the other end passes through the side wall of the pretreatment tower 1 and is coaxially fixed with the output end of the drive motor 81. The top of the rotating shaft 43 is coaxially fixed with a second bevel gear 431, and the second bevel gear 431 is meshed with the first bevel gear 821. In this embodiment, the ultraviolet light source 42 is a high-power ultraviolet lamp, such as a xenon lamp, a high-pressure mercury lamp, etc.; the photocatalyst coating 411 is a titanium dioxide nano-coating.

[0056] When the drive motor 81 rotates, it drives the drive shaft 82, which in turn drives the first bevel gear 821. The first bevel gear 821 drives the second bevel gear 431, which in turn drives the rotating shaft 43, thereby driving the catalytic carrier 41. The number of catalytic carriers 41 is related to the total coating area of ​​the photocatalytic coating 411. However, it is not advisable to have too many catalytic carriers 41, as this will cause the coating area of ​​the photocatalytic coating 411 to overflow, resulting in a significant increase in the oxidation rate of nitrogen oxides and, in turn, increasing the cost of installing the catalytic carriers 41 and the photocatalytic coating 411, as well as the burden on the drive motor 81.

[0057] Reference Figure 2 、 Figure 6 and Figure 7 The interior of the catalytic carrier plate 41 is hollow and densely covered with a plurality of ventilation holes 412. This increases the surface area available for the photocatalytic coating 411 to adhere to and the contact area with the flue gas. Furthermore, when the rotating shaft 43 rotates, a portion of the flue gas surrounding the catalytic carrier plate 41 ripples in all directions as the catalytic carrier plate 41 is moved, while another portion of the flue gas can directly pass through the ventilation holes 412 and enter the hollow structure of the catalytic carrier plate 41. This increases the turbulence of the flue gas in the pretreatment tower 1, making it easier for the flue gas to enter the interior of the catalytic carrier plate 41 through the ventilation holes 412. The flue gas that enters the catalytic carrier plate 41 has a longer residence time, allowing the nitrogen oxides therein to be more thoroughly oxidized by the photocatalytic coating 411. Furthermore, as the catalytic carrier plate 41 rotates, its rotation angle continuously changes, resulting in a more balanced distribution of ultraviolet light at each location, which can improve the overall oxidation efficiency of nitrogen oxides in the flue gas.

[0058] Reference Figure 2and Figure 6 To fully utilize the ultraviolet light in the pretreatment tower 1, a reflective film 14 is attached to the inner wall of the pretreatment tower 1 and surrounds the catalytic carrier plate 41. In this embodiment, the reflective film 14 is made of aluminum, which can reflect ultraviolet light that diffuses onto the inner wall of the pretreatment tower 1 back onto the catalytic carrier plate 41, thereby fully improving the utilization rate of the ultraviolet light.

[0059] Reference Figure 2 and Figure 3 After catalytic oxidation, nitrogen oxides in the flue gas are passed into the wet absorption box 2 through the flue gas duct assembly 3. The flue gas duct assembly 3 includes a main duct 31, a connecting duct 32, and multiple sub-ducts 33, which are connected in sequence. The end of the main duct 31 away from the sub-ducts 33 is fixedly connected to the top of the pretreatment tower 1. The end of the sub-duct 33 away from the main duct 31 extends below the liquid level in the wet absorption box 2. A waterproof and breathable membrane 331 is fixed to the bottom of the sub-duct 33.

[0060] The oxidized flue gas passes through the main air duct 31, the connecting air duct 32 and the sub-air duct 33 in sequence, and is finally discharged into the denitrification absorption liquid in the wet absorption box 2. The denitrification efficiency of the flue gas is improved by adding multiple sub-air ducts 33. In addition, the flue gas can enter the denitrification absorption liquid through the waterproof and breathable membrane 331, while the denitrification absorption liquid cannot enter the sub-air duct 33 through the waterproof and breathable membrane 331, which increases the path for the flue gas to emerge from the denitrification absorption liquid, allowing the nitrogen oxides in the flue gas to fully contact the denitrification absorption liquid, thereby making the denitrification of the flue gas more thorough.

[0061] Reference Figure 8 To detect the nitrogen oxide content in the flue gas discharged after the final denitrification treatment, a nitrogen oxide detector 211 is installed on the inner wall of the exhaust pipe 21. If the detected value does not meet the set safe emission value, the nitrogen oxide detector 211 will issue an alarm. At this time, the operator needs to reduce the rate at which the treated flue gas is introduced into the intake pipe 11, increase the illumination intensity of the ultraviolet light source 42, or replace or replenish the denitrification absorption liquid, etc., based on the actual situation on site.

[0062] The implementation principle of a photocatalyst pretreatment flue gas denitrification device in an embodiment of the present application is as follows: the flue gas to be treated is passed into the pretreatment tower 1 from the air inlet pipe 11. When the flue gas passes through the cyclone assembly 6, the larger fly ash particles in the flue gas are blocked by the guide plate 62 and fall down under the influence of their own weight. When they move upward again, they will pass through the cyclone assembly 6 along the inclined direction of the guide plate 62 to form a cyclone, and will be further blocked by the dust shield 51, thereby achieving dust reduction of the flue gas.

[0063] Subsequently, the flue gas continues to flow upward, and when passing through the filter 52, the fly ash particles remaining in the flue gas are filtered by the filter 52. At the same time, the filter 52 is cooled by absorbing heat through the condensation component, and the water vapor in the flue gas condenses into water droplets on the filter 52. The strong hydrophobicity of the first self-cleaning coating 521 realizes the self-cleaning effect of the filter 52.

[0064] When the flue gas after layer-by-layer dust reduction treatment flows to the photocatalytic system 4, the photocatalytic system 4 catalytically oxidizes the nitrogen oxides in the flue gas, and then passes into the wet absorption box 2 through the flue gas duct assembly 3. After fully contacting with the denitrification absorption liquid, the denitrification absorption liquid absorbs the nitrogen oxides in the flue gas, and the treated flue gas is finally discharged from the exhaust pipe 21.

[0065] The photocatalytic system 4 oxidizes the poorly water-soluble NO into a high-valent state, thereby increasing the water solubility of nitrogen oxides in the flue gas and thus improving the treatment efficiency of wet flue gas denitrification.

[0066] In a second aspect, the present application also discloses an intelligent monitoring method for flue gas denitrification, which is used to calculate and analyze the values ​​detected by the nitrogen oxide detector 211 and control the flue gas flow rate of the intake pipe 11, so as to maximize the flue gas flow rate while ensuring that the nitrogen oxide content in the exhaust gas from the exhaust pipe meets the standard, thereby improving the treatment efficiency of flue gas denitrification, and includes the following steps:

[0067] Step 1: collect the actual measurement value of the nitrogen oxide detector 211 in real time, compare it with the set safe emission value, and calculate the deviation value of nitrogen oxides in the exhaust gas from the exhaust pipe 21 and the change rate of the deviation value;

[0068] Assume that the safe emission value set by the nitrogen oxide detector 211 is r(t), and its actual measured value is n(t), then its deviation value is e(t)=r(t)-n(t); the change rate of the deviation value is Where t is time.

[0069] Step 2: Input the deviation value and the rate of change of the deviation of nitrogen oxides in the exhaust gas from the exhaust pipe 21 into the fuzzy controller. The fuzzy controller determines the nitrogen oxide deviation, the rate of change of the deviation, and the proportional change value Δk according to the input deviation value and the rate of change of the deviation of nitrogen oxides at the flue gas outlet according to the preset corresponding relationship. p , integral change value Δk i , differential change value Δk d The membership function of .

[0070] Step 3: According to the fuzzy control rules, output the new fuzzy set membership function and calculate the proportional change value Δk accordingly. p , integral change value Δk i , differential change value Δkd ;

[0071] Among them, the fuzzy control rules can be initially determined by analyzing and summarizing the historical data of the out-of-stock system under PID control; as the improved new system (the system that introduces fuzzy control) runs, the initially determined fuzzy control rules can be revised. The specific fuzzy control rules are:

[0072] (a) When the actual measurement value of the nitrogen oxide detector 211 deviates greatly from the set safe emission value, in order to speed up the response of the system and reduce or even eliminate the error in time, the proportional coefficient k of the PID is p The value is large; in order to prevent the differential oversaturation phenomenon that may be caused by the instantaneous increase of the deviation signal e, the PID differential parameter k d The value is small; in order to prevent the system response from having a large overshoot and causing integral saturation, the integral action should be limited, usually k i =0.

[0073] (b) When the actual measurement value of the nitrogen oxide detector 211 deviates from the set safety emission value e and the rate of change of the deviation e c When the size is in the medium range, in order to reduce overshoot, the proportional parameter k of the PID controller p The value is small, the integral parameter k i The value of is moderate, the differential parameter k d The value of has a great influence on the output response of the system, so it should be moderate;

[0074] (c) When the deviation e between the actual measured value of the nitrogen oxide detector 211 and the set safe emission value is small, k should be appropriately increased to ensure good steady-state performance of the system. p and k i The value of the PID controller should be selected taking into account the anti-interference performance of the system. d Take appropriate value: when the deviation change rate e of the actual measurement value of nitrogen oxide detector 211 and the set safe emission value c When k is small, d To take a larger value; when e c When k is larger, d The value is smaller. c The size of the deviation indicates the rate of change, e c The larger the value, the p The smaller the value of k i The larger the value.

[0075] Step 4: Use the proportional change value Δk p , integral change value Δk i , differential change value Δk dAdjust the corresponding proportional parameters, integral parameters, and differential parameters in PID in real time to obtain new PID parameters;

[0076] The above proportional change value Δk p , integral change value Δk i , differential change value Δk d The PID parameters are adjusted by transmitting them to Honeywell DCS system through communication or hard wiring. The proportional parameter change value Δk is used. p , integral parameter change value Δk i , differential parameter change value Δk d The corresponding proportional parameters, integral parameters, and differential parameters in PID are adjusted in real time, specifically: k p =k p′ +Δk p ;

[0077] k i =k i′ +Δk i ;

[0078] k d =k d′ +Δk d ;

[0079] In the above formula, k p′ is the proportional parameter before PID controller adjustment, k p is the new proportional parameter after adjustment, k i′ is the integral parameter of the PID controller before adjustment, k i is the new integral parameter after adjustment, k d′ is the differential parameter of the PID controller before adjustment, k d is the new differential parameter after adjustment.

[0080] Step 5: Based on the new scale parameter k p , new integration parameter k i , new differential parameter k d The operation output control signal u(t) is Among them, k i =k p / T i 、k d =k p T d ;

[0081] The control signal u(t) is output to the valve body control end of the flue gas flow rate of the intake pipe 11 to control the rate at which the flue gas enters the intake pipe 11, thereby controlling the content of nitrogen oxides in the flue gas after denitrification in real time, and then collecting the actual measurement value of the adjusted nitrogen oxide detector 211 to realize cyclic control.

[0082] The above are all preferred embodiments of the present application, and are not intended to limit the scope of protection of the present application. Therefore, any equivalent changes made based on the structure, shape, and principle of the present application should be included in the scope of protection of the present application.

Claims

1. A photocatalyst pretreatment flue gas denitrification device, characterized in that: include: A pretreatment tower (1), wherein the pretreatment tower (1) is provided with an air inlet pipe (11), and a photocatalytic system (4) is provided in the pretreatment tower (1), and the photocatalytic system (4) is used to oxidize nitrogen oxides in the flue gas; A wet absorption box (2), wherein a denitrification absorption liquid is provided in the wet absorption box (2), an exhaust pipe (21) and a liquid discharge pipe (22) are provided on the wet absorption box (2), and a nitrogen oxide detector (211) is provided in the exhaust pipe (21); A flue gas duct assembly (3) is used to connect the pretreatment tower (1) and the wet absorption box (2), and the gas outlet end of the flue gas duct assembly (3) is arranged below the liquid surface of the denitrification absorption liquid; The photocatalytic system (4) comprises a catalytic carrier plate (41) and an ultraviolet light source (42) arranged in the pretreatment tower (1); a photocatalytic coating (411) is provided on the surface of the catalytic carrier plate (41); The catalytic carrier plate (41) is hollow inside and is provided with a plurality of vent holes (412). There are a plurality of catalytic carrier plates (41), one end of each of the plurality of catalytic carrier plates (41) is connected to a common rotating shaft (43), and the pretreatment tower (1) is provided with a driving assembly (8) for driving the rotating shaft (43) to rotate. A reflective film (14) is provided on the inner wall of the pretreatment tower (1); The pretreatment tower (1) is provided with a dust reduction assembly (5), the dust reduction assembly (5) being arranged between the air inlet pipe (11) and the photocatalytic system (4), the dust reduction assembly (5) comprising a dust shield (51), the dust shield (51) being arranged on the inner wall of the pretreatment tower (1), and the end of the dust shield (51) away from the inner wall of the pretreatment tower (1) being arranged to be tilted downward; A cyclone assembly (6) is provided in the pretreatment tower (1), and the cyclone assembly (6) is provided between the air inlet pipe (11) and the dust shield (51). The cyclone assembly (6) comprises an inner ring plate (61), a guide plate (62) and an outer ring plate (63). One end of the guide plate (62) is fixed to the inner ring plate (61) and a plurality of guide plates are evenly arranged along the circumference of the inner ring plate (61). The other end is fixed to the outer ring plate (63). The plurality of guide plates (62) are stacked and tilted. The outer ring plate (63) is fixed to the inner wall of the pretreatment tower (1). An ash hopper (12) is provided at the bottom of the pretreatment tower (1). The ash hopper (12) is communicated with the interior of the pretreatment tower (1). A discharge valve (121) is provided at the bottom of the ash hopper (12). The flue gas duct assembly (3) comprises a main duct (31), a connecting duct (32) and a sub-duct (33) which are connected in sequence. One end of the main duct (31) away from the sub-duct (33) is connected to the top of the pretreatment tower (1). One end of the sub-duct (33) away from the main duct (31) extends below the liquid level of the wet absorption box (2). A waterproof and breathable membrane (331) is provided at the bottom of the sub-duct (33).

2. The photocatalytic pretreatment flue gas denitrification device according to claim 1, characterized in that: The dust reduction assembly (5) further comprises a filter screen (52) for filtering fly ash in the flue gas, wherein the filter screen (52) is arranged between the dust shield (51) and the photocatalytic system (4), the lower surface of the filter screen (52) is provided with a first self-cleaning coating (521), and the inclined top surfaces of the dust shield (51) and the guide plate (62) are provided with a second self-cleaning coating (511).

3. The photocatalytic pretreatment flue gas denitrification device according to claim 2, characterized in that: A cold source assembly (7) is provided on the filter screen (52), and the cold source assembly (7) comprises a cold flow pipe (71) provided on the filter screen (52), the cold flow pipe (71) being arranged in a continuously bent manner, a liquid inlet (711) being provided at one end of the cold flow pipe (711), and a liquid outlet (712) being provided at the other end, the liquid inlet (711) being in communication with an external tap water pipe, and the liquid outlet (712) being provided above the filter screen (52).

4. An intelligent monitoring method for a photocatalytic pretreatment flue gas denitrification device according to any one of claims 1 to 3, characterized in that: The steps include: S1: collecting the actual measurement value of the nitrogen oxide detector (211) in real time, comparing it with the set safe emission value, and calculating the deviation value of nitrogen oxides in the exhaust gas from the exhaust pipe (21) and the change rate of the deviation value; S2: Input the deviation value and the rate of change of the nitrogen oxides in the exhaust gas from the exhaust pipe (21) into the fuzzy controller to determine the nitrogen oxide deviation, the rate of change of the deviation, and the proportional change value Δk p , integral change value Δk i , differential change value Δk d The membership function of S3: According to the fuzzy control rules, output the new fuzzy set membership function and calculate the proportional change value Δk accordingly p , integral change value Δk i , differential change value Δk d ; S4: Use proportional change value Δk p , integral change value Δk i , differential change value Δk d Adjust the corresponding proportional parameters, integral parameters, and differential parameters in PID in real time to obtain new PID parameters; S5: According to the new PID parameters, the opening and closing degree of the valve body at the intake pipe (11) is controlled to control the flue gas flow in the intake pipe (11).

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